Controlled release of surfactants for enhanced oil recovery

ABSTRACT

A sparingly soluble sulfonate-metal salt particle includes the metal ion salt of an alkyl aryl sulfonate, the metal ion salt of a petroleum sulfonate and a hydrophobically modified hydrophilic polymer, and has an average particle size diameter in a range of from about 50 nm to about 450 nm and is sparingly soluble in water at room temperature. A method of producing a sparingly soluble sulfonate-metal salt particle includes the steps of introducing an aqueous solution containing a metal ion salt into a reactor, introducing an aqueous solution containing a sulfonate surfactant and a polymer into the reactor, and operating the reactor such that the sparingly soluble sulfonate-metal salt particle forms from the interaction of the metal ion from the salt, the sulfonate surfactant and the polymer.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/407,799, filed Jan. 17, 2017, which is a divisional of U.S. patentapplication Ser. No. 14/043,403, filed Oct. 1, 2013, now U.S. Pat. No.9,580,639 issued on Feb. 28, 2017, which is a continuation-in-part ofU.S. patent application Ser. No. 13/184,974, filed Jul. 18, 2011, nowU.S. Pat. No. 8,946,132 issued on Feb. 3, 2015. For purposes of UnitedStates patent practice, this application incorporates the contents ofall the prior applications by reference in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The field of invention relates to compositions, delivery systems, andmethods suitable for the enhanced oil recovery process.

2. Description of the Related Art

Surfactants are used in enhanced oil recovery (EOR) processes. Thepresence of a surfactant at the water/oil interface facilitates oilrecovery.

Conventional methods feed surfactant solution into the reservoirdirectly to maximize the surfactant dose. The active surfactant isreadily consumed at the oil-water interface. Surfactants and otherchemicals are mixed with water and driven into the reservoir.

Significant amount of surfactant is lost due to adsorption to the rockof the formation before it has a chance to encounter residual oil.Often, surfactant molecules, especially anionic surfactants, adsorb intothe rock before it interacts with oil. Adsorption of the surfactant intothe formation results in a reduction in the effective amount ofsurfactant useful for mobilizing the oil. The adsorption problem worsenswhen anionic surfactants encounter carbonate rock, which acts as a Lewisacid. The extent of surfactant adsorption depends on the type of rock,pore surface area, water salinity and the type of surfactant. Ingeneral, roughly one milligram of surfactant adsorbs into one gram ofrock. In addition to adsorption, some surfactants precipitate from thesaline water with cations from the rock. In either case, somesurfactants are lost before they have a chance to solubilize oil.

To overcome the adsorption and precipitation problems, increasing theamount of surfactants in water allows for the extra surfactants to beabsorbed by the rock and still deliver remaining surfactants to theoil/water interface. However, the additional surfactant cost isprohibitive. Others use sacrificial chemicals to passivate the rocksurface such that surfactant adsorption is mitigated before application.

When a slug of surfactant mixed in a polymer solution is introduced intothe reservoir, the surfactant quickly deposits and, depending on theamount used, may be saturated on the oil-water interface. The oil, thussolubilized by the surfactant, can be recovered. Unfortunately, residualoil that lies behind the initial oil-water interface has less a chanceof interacting with the surfactant and may remain immobilized

Overall, the approaches fail to maintain a constant concentration ofsurfactant over an extended period in the formation. It would be idealto have a sustained and constant concentration of free surfactant at thewater/oil interface to prolong and improve oil recovery while avoidingadsorption into the formation.

SUMMARY OF THE INVENTION

One embodiment of the invention is a composition for the controlledrelease of surfactants in oil recovery operation, the composition beingmade of an aqueous sulfonate solution and a metal salt selected fromaluminium nitrate nonahydrate, calcium chloride dehydrate, magnesiumchloride hexahydrate, cobalt chloride hexahydrate, and other metalsalts, wherein the mean diameter of the formed sparingly solublesulfonate surfactant-metal salt particle is between 20 nm and 100 nm andsolubility of the sparingly soluble sulfonate surfactant-metal saltparticle is less than 100 ppm at room temperature. In anotherembodiment, the sparingly soluble sulfonate surfactant-metal saltparticle additionally contains hydrolyzed polyacrylamide.

Another embodiment of the invention is a hydrocarbon recoverycomposition comprising a composition which comprises an aqueoussulfonate solution and a metal salt selected from aluminium nitratenonahydrate, calcium chloride dehydrate, magnesium chloride hexahydrate,cobalt chloride hexahydrate, and other metal salts, wherein the meandiameter of the formed sparingly soluble sulfonate surfactant-metal saltparticle is between 20 nm and 100 nm and solubility of the sparinglysoluble sulfonate surfactant-metal salt particle is less than 100 ppm atroom temperature. In another embodiment, the sparingly soluble sulfonatesurfactant-metal salt particle additionally contains hydrolyzedpolyacrylamide.

Another embodiment of the invention is a delivery system for controllingthe release of surfactants in hydrocarbon recovery operation, thedelivery system comprising an aqueous sulfonate solution and a saltselected from aluminium nitrate nonahydrate, calcium chloride dehydrate,magnesium chloride hexahydrate, cobalt chloride hexahydrate, and othermetal salts, wherein the mean diameter of the formed sparingly solublesulfonate surfactant-metal salt particle is between 20 nm and 100 nm andsolubility of the sparingly soluble sulfonate surfactant-metal saltparticle less than 100 ppm at room temperature; in an amount operablesuch that the sulfonate in the aqueous solution reduces surface tensionof the hydrocarbon so that oil recovery is increased. In anotherembodiment, the sparingly soluble sulfonate surfactant-metal saltparticle further contains hydrolyzed polyacrylamide.

Another embodiment of the invention is a method of delivering acontrolled release of surfactants composition, the method including thefollowing the steps, such as: (1) delivering an aqueous solution into areservoir, the aqueous solution containing an aqueous sulfonatesolution; and a metal salt selected from aluminium nitrate nonahydrate,calcium chloride dehydrate, magnesium chloride hexahydrate, cobaltchloride hexahydrate, and other metal salts; wherein the mean diameterof the formed sparingly soluble sulfonate surfactant-metal salt particleis between 20 nm and 100 nm and solubility of the sparingly solublesulfonate surfactant-metal salt particle is less than 100 ppm at roomtemperature; and (2) delivering water to the reservoir.

Another embodiment of the invention is a method of treating ahydrocarbon containing formation by (a) providing a hydrocarbon recoverycomposition to at least a portion of the hydrocarbon containingformation, wherein the hydrocarbon recovery composition comprises (1) anaqueous sulfonate solution and (2) a metal salt selected from aluminiumnitrate nonahydrate, calcium chloride dehydrate, magnesium chloridehexahydrate, cobalt chloride hexahydrate, and other metal salts; whereinthe mean diameter of the sparingly soluble sulfonate surfactant-metalsalt particle is between 20 nm and 100 nm and solubility of thesparingly soluble sulfonate surfactant-metal salt particle is less than100 ppm at room temperature; and (b) allowing the hydrocarbon recoverycomposition to interact with hydrocarbons in the hydrocarbon containingformation.

A method of producing a sparingly soluble sulfonate surfactant-metalsalt particle includes the steps of introducing an aqueous solutioncontaining a metal ion salt into a reactor. The method includesintroducing an aqueous solution containing a sulfonate surfactant and apolymer into the reactor. The method includes operating the reactor suchthat the sulfonate surfactant-metal salt particle forms from theinteraction of the metal ion from the salt, the sulfonate surfactant andthe polymer. The sulfonate surfactant-metal salt particle has an averageparticle size diameter in a range of from about 50 nm to about 450 nmand is sparingly soluble in water at room temperature.

A sparingly soluble sulfonate surfactant-metal salt particle includes ametal ion salt of an alkyl aryl sulfonate, a metal ion salt of apetroleum sulfonate and a hydrophobically modified hydrophilic polymer.The sulfonate surfactant-metal salt particle has an average particlesize diameter in a range of from about 50 nm to about 450 nm and issparingly soluble in water at room temperature.

Anionic surfactants can form salts some cations in situ. Salt formationis considered problematic and undesirable during enhanced oil recovery(EOR) since the formation of surfactant salts with ions present in thewater or the rock results in the immediate loss of surfactants forextracting hydrocarbons. However, surfactant-metal salts can beengineered and used in such ways as to contribute to the EOR process forthe long-term.

There are a number of technical hurdles to overcome for forming asparingly soluble surfactant-metal salt that is useful for EORprocesses. For example, the sparingly soluble surfactant-metal saltparticles or capsules should be small—200 nm or less. This permits thesurfactant-metal salt particles to travel into the formation and throughthe pores in the reservoir. The surfactant-metal salt particle size canbe manipulated by controlling the nucleation rate for the precipitationof the particles. Another way to manipulate the particle size is to usea mechanical milling device to grind down larger particles. In addition,nano-sized particles have to be dispersible within in the reservoirenvironment conditions, that is, up to 100° C. and with 25 wt. %salinity of aqueous solution.

In the pharmaceutical and other industries, active ingredients are oftendelivered to a targeted area in a controlled release fashion such thatone dose of active ingredient can sustain efficacy for a longer period.We intend to apply similar techniques to the delivery of surfactants.Ideally, surfactants will be delivered in a controlled manner andreleased at the oil/water interface. The delivered salt particle is akinto micro reservoirs of surfactant that feed the surfactant molecules tothe oil/water interface at a constant concentration and a constant rate.As a result, residual oil at the treatment site is continuallysolubilized.

Anionic surfactants, such as sulfonates, are converted intosurfactant-metal salt particles. The surfactant has a negative chargewhich reacts with the positively charged cations. Depending on thenature of surfactant anions and metal cations, some of the resultingsurfactant salts are partially or sparingly soluble in water. Thesparingly soluble surfactant-metal salts, being only slightly soluble inwater, supply surfactant at a limited and controlled rate given thesurfactant concentration in the water. This provides a continuous, lowlevel of surfactant concentration at the oil/water interface of thetreatment site for extended periods.

The sparingly soluble surfactant-metal salt nanoparticles can supply aconstant flux of surfactant molecules into the surfactant solution.Because of this sustained supply of fresh surfactant molecules, moreresidual oil may be recovered over a period of time. The inventionprovides colloidal surfactant salts that maintain a constant freesurfactant concentration in the surfactant solution. Because of thisconstant and sustained supply of fresh surfactant molecules moreresidual oil may be recovered.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Specification, which includes the Summary of Invention, BriefDescription of the Drawings and the Detailed Description of thePreferred Embodiments, and the appended Claims refer to particularfeatures (including process or method steps) of the invention. Those ofskill in the art understand that the invention includes all possiblecombinations and uses of particular features described in theSpecification. Those of skill in the art understand that the inventionis not limited to or by the description of embodiments given in theSpecification. The inventive subject matter is not restricted exceptonly in the spirit of the Specification and appended Claims.

Those of skill in the art also understand that the terminology used fordescribing particular embodiments does not limit the scope or breadth ofthe invention. In interpreting the Specification and appended Claims,all terms should be interpreted in the broadest possible mannerconsistent with the context of each term. All technical and scientificterms used in the Specification and appended Claims have the samemeaning as commonly understood by one of ordinary skill in the art towhich this invention belongs unless defined otherwise.

As used in the Specification and appended Claims, the singular forms“a”, “an”, and “the” include plural references unless the contextclearly indicates otherwise. The verb “comprises” and its conjugatedforms should be interpreted as referring to elements, components orsteps in a non-exclusive manner. The referenced elements, components orsteps may be present, utilized or combined with other elements,components or steps not expressly referenced. The verb “couple” and itsconjugated forms means to complete any type of required junction,including electrical, mechanical or fluid, to form a singular objectfrom two or more previously non-joined objects. If a first devicecouples to a second device, the connection can occur either directly orthrough a common connector. “Operable” and its various forms means fitfor its proper functioning and able to be used for its intended use.

Where the Specification or the appended Claims provide a range ofvalues, it is understood that the interval encompasses each interveningvalue between the upper limit and the lower limit as well as the upperlimit and the lower limit. The invention encompasses and bounds smallerranges of the interval subject to any specific exclusion provided.

Where the Specification and appended Claims reference a methodcomprising two or more defined steps, the defined steps can be carriedout in any order or simultaneously except where the context excludesthat possibility.

When a patent or a publication is referenced in this disclosure, thereference is incorporated by reference and in its entirety to the extentthat it does not contradict statements made in this disclosure.

Sparingly Soluble Sulfonate-Metal Salts

The compositions and delivery systems disclosed provide a means toslowly release sulfonate surfactant in an aqueous solution, maintain thelocal sulfonate surfactant concentration at a constant level, andsustain the release of the sulfonate surfactant over a long period. Therock in a reservoir is porous with a wide pore size distribution. Porescan be as small as 1 micron and as large as 20 micron. A particle is adiscrete entity of solid matter in a dispersed state with a diameter ator less than about 50 micrometers (50 μm). Larger size particles couldbe trapped by the pores. The sparingly soluble sulfonate-metal saltparticles can traverse through pores of this size. An embodiment of thesparingly soluble sulfonate-metal salt particles has an average particlesize diameter in a range of from about 50 nm to about 200 nm.

Anionic surfactant salts that are precipitated by different cations havedifferent solution solubility, which affects the surfactant saltparticle size and the amount of sulfonate surfactant in the aqueoussolution. In other words, the free surfactant concentration in theformed surfactant solution can be regulated by the choice of thesurfactant salt to introduce into the aqueous solution. Sparinglysoluble surfactant-metal salt particles can be made smaller than 200 nm,smaller than 100 nm, or smaller than 50 nm.

The sulfonate-metal salt particles are sparingly soluble. A saturatedsolution of a sparingly soluble salt in water (solubility of less than10⁻³ mol/L) may be considered to exist in a dynamic equilibrium of twoopposing reactions. The dissolution of the solid salt and thecrystallization of the salt are the two opposing reactions. When therates of the two reactions are equal there is dynamic equilibrium. Forexample, when the sulfonate-metal salt has a solubility of 100 ppm inwater, and 1.0 weight percent of sulfonate-metal salt is added in 1liter of water, the sulfonate surfactant concentration in the aqueoussolution is held constant at 100 ppm. Sulfonate-metal salt introducedinto water releases sulfonate surfactant until the sulfonate surfactantin the aqueous solution achieves a concentration of 100 ppm, when adynamic equilibrium forms between the sulfonate solution and thesulfonate-metal salt. An embodiment of the sparingly solublesulfonate-metal salt particles has a solubility in a range of from about50 parts-per-million (ppm) to about 300 ppm in water at roomtemperature. An embodiment of the sparingly soluble sulfonate-metal saltparticles has a solubility in a range of from about 50 ppm to about 200ppm in water at room temperature. An embodiment of the sparingly solublesulfonate-metal salt particles has a solubility in a range of from about50 ppm to about 100 ppm in water at room temperature.

A dispersion of sparingly soluble sulfonate-metal salt nanoparticleswithin an aqueous solution of sulfonate surfactant, when not in contactwith a hydrocarbon, is in dynamic equilibrium. The replenishment of thesulfonate surfactant into the aqueous solution is driven bythermodynamic equilibrium between the solid, sparingly solublesurfactant-metal salt and the soluble surfactant in the aqueoussolution.

The transport of the sulfonate surfactant from the surfactant-metal saltinto the surfactant solution depends on the concentration of freesurfactant already present in the solution, the equilibrium between thesparingly soluble surfactant-metal salt particles, and the rate ofadsorption of free surfactant by present hydrocarbons. For example, ifthe sulfonate surfactant in solution is consumed upon contacting oilwithin a day, then another 100 ppm of sulfonate surfactant isreplenished into the solution from the solid surfactant salt particles.In other words, the 100 ppm free surfactant concentration is maintainedin the aqueous sulfonate solution by the presence of the sparinglysoluble sulfonate-metal salt particles. The sparingly solublesulfonate-metal salt particles contain sufficient amount of sulfonatesurfactant to allow for sustained release from several hours to severaldays

The aqueous solution in which the sparingly soluble sulfonate-metal saltparticles is dispersed can range from de-ionized water to saline water,with salinity as high as 25 weight percent. The concentration of thesulfonate surfactant in the solution is dependent on the sparingsolubility of the sulfonate-metal salt.

The combination of sparingly soluble sulfonate-metal salt nanoparticleswithin an aqueous solution of sulfonate surfactant or water is adispersion. A dispersion consists of a fine insoluble or only slightlysoluble particles distributed throughout a continuous medium. A“dispersion” is a two-phase system where one phase consists of finelydivided particles (often in the colloidal size range) distributedthroughout a bulk substance, the salt particles being the disperse orinternal phase and the bulk substance the continuous or external phase.A dispersion is usually polydisperse—the dispersed salt particlesusually have different sizes and shapes. A solid-in-liquid colloidaldispersion (loosely called solutions) can be precipitated. In the caseof the sparingly soluble surfactant salts, the surfactant saltsprecipitate out of the solution. Larger particles will graduallycoalesce and settle out.

The sparingly soluble surfactant-metal salt particle includes a metalion salt of an anionic surfactant and a polymer. Useful metal ionsinclude aluminum, calcium, magnesium, cobalt, zinc, barium, coppernitrate, and strontium. Useful anionic surfactants include alkylsulfonates, alkyl aryl sulfonates, including dodecyl benzene sulfonate,alkyl aryl ether phosphates, alkyl ether phosphates, alky ethersulfates, and alkyl sulfates, and petroleum sulfonates. Useful polymersinclude partially hydrolyzed polyacrylamide, xanthan gum and polyvinylpyrrolidone, hydrophobically modified hydrophilic polymers, includingpolymers made from monomers of dimethylaminoethyl methacrylate andcetyldimethylammoniumethyl methacrylate halide, polyvinyl acetate,polyvinyl alcohol and gelatins.

An embodiment of the sparingly soluble surfactant-metal salt particleincludes the metal ion salt of an alkyl aryl sulfonate, the metal ionsalt of a petroleum sulfonate and a hydrophobically modified hydrophilicpolymer and has an average particle size diameter in a range of fromabout 50 nm to about 450 nm. An embodiment of the sparingly solublesurfactant-metal salt particle is where the petroleum sulfonate includessulfonated benzenoid, cycloaliphatic, paraffinic hydrocarbons, andcombinations thereof.

Method of Preparation

In an embodiment of the method of preparation of the sparingly solublesurfactant-metal salt particle, about 0.1 to about 2.0 weight percent ofpolymer is mixed with about 0.05 to about 5 weight percent of a metalion salt at a temperature between about 0° C. and about 120° C. Examplesof useful polymers include partially hydrolyzed polyacrylamide, xanthangum and polyvinyl pyrrolidone. Examples of useful metal ion saltsinclude aluminum nitrate nonahydrate, calcium chloride dihydrate,magnesium chloride hexahydrate, cobalt chloride hexahydrate, zincchloride, barium chloride dihydrate, copper nitrate, and strontiumchloride hexahydrate. To the polymer/salt mixture about 0.05 to about 5weight percent of anionic surfactant is then added with vigorousstirring at temperatures about 0° C. and about 90° C. Examples of usefulanionic surfactants include alkyl sulfonates, alkyl aryl sulfonates,alkyl aryl ether phosphates, alkyl ether phosphates, alky ethersulfates, and alkyl sulfates.

An additional example of a useful metal ion salt includes copper nitratehemi(pentahydrate).

Additional examples of useful polymers include polyvinyl acetate,polyvinyl alcohol and gelatins. Another useful polymer is ahydrophobically modified hydrophilic polymer. An example of acommercially-available product that contains a hydrophobically modifiedhydrophilic polymer is HPT-1™ from Halliburton Energy Services. Althoughnot intending to be bound by theory, it is believed that thehydrophobically modified hydrophilic polymer present in HPT-1 is apolymer formed from the monomers of dimethylaminoethyl methacrylate andcetyldimethylammoniumethyl methacrylate halide.

Alkyl sulfonates are primary and secondary paraffin sulfonates (PS andSAS) and α-olefin sulfonates (AOS). Alkyl aryl sulfonates include alkylbenzene sulfonates such as dodecyl benzene sulfonate, which is a linearalkyl benzene (LAB) sulfonate surfactant. The alkyl sulfonates and thealkyl aryl sulfonates do not include any other heteroatoms except forthe sulfonate functional group.

Another example of a useful anionic surfactant is a sodium sulfonatethat is prepared by treating a petroleum fraction, such as a heavynaphtha, lube oil, white oil or a vacuum distillation cut containingC₃₀₋₄₀ PNAs, with sulfur trioxide (SO₃). The resulting “petroleumsulfonate” is a mixture that can comprise sulfonated benzenoid (bothalkyl aryl and aryl), cycloaliphatic and paraffinic (alkyl) hydrocarbonsin various ratios to one another depending on the nature of the sourcepetroleum fraction. Another benefit is that the produced petroleumsulfonate is both water and hydrocarbon soluble. An example of acommercially-available product that contains petroleum sulfonate isPETRONATE® EOR-2095 sodium sulfonate from Chemtura.

The size of the sparingly soluble surfactant-metal salt particle can becontrolled by the addition rates of anionic surfactant and the metalsalt while in aqueous solution. Since the oil reservoir pore sizes vary,a distribution of different particle sizes can be used accordingly tohelp oil recovery throughout a hydrocarbon-bearing formation. Thesparingly soluble surfactant-metal salt particles can be polydisperse.

Process variables including temperature, flow rate of introducedreactants relative to the reactor volume, concentration of components,stirring rate in a batch reactor can all have an effect on controllingthe particle size of the sparingly soluble surfactant-metal saltparticle such that the average particle size diameter of about 50 nm toabout 450 nm is achieved. For example, the attributes of the introducedaqueous solution of the metal ion salt affects the particle size of thesulfonated surfactant salt particle. An embodiment of the method ofproducing a sparingly soluble surfactant-metal salt particle includeswhere the metal ion salt concentration is in a range of from about 0.1to about 20 wt. % of the aqueous solution containing the metal ion salt.Where the reactor has a fixed volume, an embodiment of the methodincludes where the aqueous solution containing the metal ion salt has aresidence time in a range of from about 0.33 minutes to about 3 minutesin the reactor.

The attributes of the introduced aqueous solution containing thesulfonate surfactant and the polymer affects the particle size of thesulfonated surfactant salt particle. An embodiment of the method ofproducing a sparingly soluble surfactant-metal salt particle includeswhere the sulfonate surfactant is selected from the group consisting ofan alkyl sulfonate, an alkyl aryl sulfonate, and combinations thereof.An embodiment of the method includes where the alkyl aryl sulfonate isdodecyl benzene sulfonate. An embodiment of the method includes wherethe sulfonate surfactant comprises a mixture of a petroleum sulfonateand dodecyl benzene sulfonate. An embodiment of the method includeswhere the polymer is selected from the group consisting ofpolyacrylamide, polyvinyl acetate, polyvinyl alcohol, xanthan gum,gelatins, a hydrophobically modified hydrophilic polymer, andcombinations thereof. An embodiment of the method includes where thesulfonated surfactant salt particle comprises the metal ion salt ofdodecyl benzene sulfonate, the metal ion salt of sulfonated petroleumand a hydrophobically modified hydrophilic polymer. An embodiment of themethod includes where the sulfonate surfactant concentration is in arange of from about 0.1 to about 20 wt. % of the aqueous solutioncontaining the sulfonate surfactant and the polymer. An embodiment ofthe method includes where the polymer concentration is in a range offrom about 0.1 to about 20 wt. % of the aqueous solution containing thesulfonate surfactant and the polymer. Where the reactor has a fixedvolume, an embodiment of the method includes where the solutioncontaining the sulfonate surfactant and the polymer are introduced intothe reactor such that the sulfonate surfactant and the polymer have aresidence time in a range of from about 0.17 minutes to about 1.5minutes in the reactor.

An embodiment of the method of producing a sparingly solublesurfactant-metal salt particle includes where the solution containingthe sulfonate surfactant and the polymer is a non-aqueous solution.

An embodiment of the method of producing a sparingly solublesurfactant-metal salt particle includes where the reactor is operatedsuch that a temperature is maintained in a range of from about 0° C. toabout 95° C. during sparingly soluble surfactant-metal salt particleformation. An embodiment of the method includes where the reactor is abatch-type mixing reactor and the reactor is maintained at a mixing rateof 10 to 5,000 RPM during sulfonate surfactant salt particle formation.An embodiment of the method includes where the reactor is operated suchthat the sulfonated surfactant salt particle has an average particlesize diameter in a range of from about 50 nm to about 200 nm.

In an embodiment of the method of preparation, between about 0.05 andabout 5 weight percent a metal ion salt at temperatures about 0° C. andabout 90° C. is added to about 0.05 to about 5 weight percent of alkylsulfonate with vigorous stirring.

Method of Use

An embodiment of the method of treating a hydrocarbon containingformation includes introducing a slug of solution containing nanoparticles of surfactant salts, polymer and water into the reservoir. Theslug is then followed by a water flood. The rates of the floods areadjusted such that an optimum amount of oil is recovered.

In an embodiment of the oil recovery operation, an aqueous dispersionconsisting 0.05 to 5 weight percent of polymer, and 0.05 to 5 weightpercent of the anionic surfactant salt particles with mean particle sizeless than 200 nm, is injected into an oil containing reservoir. Theinjected dispersion is then maintained in the reservoir for 1 hour to1,000 hours. After the shut in period, the dispersion slug is followedby water flooding.

EXAMPLES

Examples of specific embodiments facilitate a better understanding ofcompositions and methods of forming sparingly soluble surfactant-metalsalt particles and dispersions of sparingly soluble surfactant-metalsalt particles in aqueous surfactant solutions useful for EOR. In no wayshould the Examples limit or define the scope of the invention.

To determine whether the precipitating anionic surfactant salt particlesize for a given preparation is under 200 nm, the particle size ismeasured by Zetasizer, such as for example, one made by MalvernInstrument. The number averaged particle size of the anionic surfactantsalt particles is determined from the sample.

The resulting salt dispersion is centrifuged and filtered. Thesupernatant sulfonate concentration in the supernatant is measured bythe Total Carbon Analyzer.

Example 1

This example demonstrates that small particle size aluminum sulfonatesalt can be prepared. Two ml of 0.3% partially hydrolyzed polyacrylamidewas mixed with two mL of 1% aluminum nitrate nonahydrate at 0° C.Nineteen mL of 0.1 wt. % (1000 ppm) PETRONATE® EOR-2095 was then addedwith vigorous stirring. The resulting precipitate particle size wasmeasured by the Zetasizer and number averaged particle size wasdetermined to be 109 nm.

Example 2

This example demonstrates that small particle size calcium sulfonatesalt can be prepared. This example is similar to Example 1, except that1% calcium chloride dehydrate was used instead of aluminum nitratenonahydrate. The resulting precipitate particle size was 73 nm.

Example 3

This example demonstrates that small particle size magnesium sulfonatesalt can be prepared. This example is similar to Example 1, except that1% magnesium chloride hexahydrate was used instead of aluminum nitratenonahydrate. The resulting precipitate particle size was 62 nm.

Example 4

This example demonstrates that small particle size cobalt sulfonate saltcan be prepared. This example is similar to Example 1, except that 1%cobalt chloride hexahydrate was used instead of aluminum nitratenonahydrate. The resulting precipitate particle size was 87 nm.

Example 5

This example demonstrates that the free sulfonate concentration in thesupernatant can be modulated by the presence of sulfonate salt. Thisexample is similar to Example 1, except that no partially hydrolyzedpolyacrylamide solution was added. The resulting salt dispersion wascentrifuged and filtered. The supernatant sulfonate concentration in thesupernatant was measured by the Total Carbon Analyzer. It was found thatthe supernatant contained 63 parts per million of sulfonate. In otherwords, initial surfactant concentration of 1,000 ppm was reduced to aconstant free sulfonate concentration in the supernatant of 63 ppm.

Example 6

This example demonstrates that the free sulfonate concentration in thesupernatant can be modulated by the presence of sulfonate salt. Thisexample is similar to Example 5, except that calcium chloride dihydrate,instead of aluminum nitrate nonahydrate, was used. The resulting saltdispersion was centrifuged and filtered. The supernatant sulfonateconcentration in the supernatant was measured by the Total CarbonAnalyzer. It was found that the supernatant contained 83 parts permillion of sulfonate. In other words, initial surfactant concentrationof 1,000 ppm was reduced to a constant free sulfonate concentration inthe supernatant of 83 ppm.

Example 7

This example demonstrates that the free sulfonate concentration in thesupernatant can be modulated by the presence of sulfonate salt. Thisexample is similar to Example 5, except that magnesium chloridehexahydrate, instead of aluminum nitrate nonahydrate, was used. Theresulting salt dispersion was centrifuged and filtered. The supernatantsulfonate concentration in the supernatant was measured by the TotalCarbon Analyzer. It was found that the supernatant contained 300 partsper million of sulfonate. In other words, initial surfactantconcentration of 1,000 ppm was reduced to a constant free sulfonateconcentration in the supernatant of 300 ppm.

Example 8

This example demonstrates that the free sulfonate concentration in thesupernatant can be modulated by the presence of sulfonate salt. Thisexample is similar to Example 5, except that cobalt chloridehexahydrate, instead of aluminum nitrate nonahydrate, was used. Theresulting salt dispersion was centrifuged and filtered. The supernatantsulfonate concentration in the supernatant was measured by the TotalCarbon Analyzer. It was found that the supernatant contained 106 partsper million of sulfonate. In other words, initial surfactantconcentration of 1,000 ppm was reduced to a constant free sulfonateconcentration in the supernatant of 106 ppm.

Example 9

Example 9 demonstrates that the particle size of the cobalt sulfonatesalt can be controlled by the anionic sulfonate surfactant and by cobaltsalt fluid introduction flow rates. A reactor containing 30 mL of waterwas stirred vigorously at room temperature. A 30 mL of 1 wt. % cobaltchloride hexahydrate aqueous solution was pumped into the reactor at arate of about 10 mL/min. At the same time, a 60 mL non-aqueous solutioncontaining 0.5 wt. % PETRONATE® EOR-2095 and 5 wt. % HPT-1™ wassimultaneously pumped into the reactor at a rate of about 20 mL/min. Theresulting average particle size diameter for the described run wasdetermined to be about 232 nm. Table 1 summarizes the average cobaltsulfonate surfactant salt particle size as a function of three differentintroduction feed flow rates of the cobalt salt solution and thepetroleum sulfonate surfactant solution. The cobalt sulfonate surfactantsalt particle sizes were measured by a Field Flow Fractionationinstrument (Model AF2000; Postnova; Germany).

TABLE 1 Cobalt ion and petroleum sulfonate solution flow rates,residence times and average cobalt sulfonate surfactant salt particlesize for three given sets of feed flow rates. Sulfonate SulfonateAverage Co ion surfactant Co ion surfactant Co-sulfonate solution sol'nsol'n sol'n surfactant salt volume volume residence residence particlesize flow rate flow rate time time diameter mL/min mL/min min min nm 1020 3 1.5 232 30 60 1 0.5 284 90 180 0.33 0.17 68

Example 10

Example 10 demonstrates that the particle size of the zinc sulfonatesalt can be controlled by the anionic surfactant and the zinc salt fluidintroduction flow rates. A reactor containing 30 mL of water was stirredvigorously at room temperature. A 30 mL of 1 wt. % zinc chloride aqueoussolution was pumped into the reactor at a rate of about 10 mL/min. Atthe same time, a 60 mL non-aqueous solution containing 0.5 wt. %PETRONATE® EOR-2095 and 5 wt. % HPT-1 was simultaneously pumped into thereactor at a rate of about 20 mL/min. The resulting average particlesize diameter for the described run was determined to be about 170 nm.Table 2 summarizes the average zinc sulfonate surfactant salt particlesize as a function of three different introduction feed flow rates ofthe zinc salt solution and the petroleum sulfonate surfactant solution.The zinc sulfonate surfactant salt particle sizes were measured usingthe Field Flow Fractionation of Example 9.

TABLE 2 Zinc ion and petroleum sulfonate solution flow rates, residencetimes and average zinc sulfonate surfactant salt particle size for threegiven sets of feed flow rates. Sulfonate Sulfonate Average Zn ionsurfactant Zn ion surfactant Zn-sulfonate solution sol'n sol'n sol'nsurfactant salt volume volume residence residence particle size flowrate flow rate time time diameter mL/min mL/min min min nm 10 20 3 1.5170 30 60 1 0.5 269 60 120 0.5 0.25 200

Example 11

Example 11 demonstrates that the particle size of the aluminum sulfonatesalt can be controlled by the anionic surfactant and the aluminum saltfluid introduction flow rates. A reactor containing 30 mL of water wasstirred vigorously at room temperature. A 30 mL of 1 wt. % aluminumnitrate nonahydrate aqueous solution was pumped into the reactor at arate of about 10 mL/min. At the same time, a 60 mL non-aqueous solutioncontaining 0.5 wt. % PETRONATE® EOR-2095 and 5 wt. % HPT-1 wassimultaneously pumped into the reactor at a rate of about 20 mL/min. Theresulting average particle size diameter for the described run wasdetermined to be about 430 nm. Table 3 summarizes the average aluminumsulfonate surfactant salt particle size as a function of three differentintroduction feed flow rates of the aluminum salt solution and thepetroleum sulfonate surfactant solution. The aluminum sulfonatesurfactant salt particle sizes were measured using the Field FlowFractionation of Example 9.

TABLE 3 Aluminum ion and petroleum sulfonate solution flow rates,residence times and average aluminum sulfonate surfactant salt particlesize for three given sets of feed flow rates. Sulfonate SulfonateAverage Al ion surfactant Al ion surfactant Al-sulfonate solution sol'nsol'n sol'n surfactant salt volume volume residence residence particlesize flow rate flow rate time time diameter mL/min mL/min Min min nm 1020 3 1.5 430 60 120 0.5 0.25 374 90 180 0.33 0.17 275

Example 12

Example 12 demonstrates that the particle size of the copper sulfonatesalt can be controlled by the anionic surfactant and the copper saltfluid introduction flow rates. A reactor containing 30 mL of water wasstirred vigorously at room temperature. A 30 mL of 1 wt. % coppernitrate hemi(pentahydrate) aqueous solution was pumped into the reactorat a rate of about 30 mL/min. At the same time, a 60 mL non-aqueoussolution containing 0.5 wt. % PETRONATE® EOR-2095 and 5 wt. % HPT-1™ wassimultaneously pumped into the reactor at a rate of about 20 mL/min. Theresulting average particle size diameter for the described run wasdetermined to be about 366 nm. Table 4 summarizes the average coppersulfonate surfactant salt particle size as a function of three differentintroduction feed flow rates of the copper salt solution and thepetroleum sulfonate surfactant solution. The copper sulfonate surfactantsalt particle sizes were measured using the Field Flow Fractionation ofExample 9.

TABLE 4 Copper ion and petroleum sulfonate solution flow rates,residence times and average copper sulfonate surfactant salt particlesize for three given sets of feed flow rates. Cu ion Sulfonate SulfonateAverage solution surfactant Cu ion surfactant Cu-sulfonate volume sol'nsol'n sol'n surfactant salt flow volume residence residence particlesize rate flow rate time time diameter mL/min mL/min Min min nm 30 60 10.5 366 60 120 0.5 0.25 219 90 180 0.33 0.17 199

What is claimed is:
 1. A method for treating a hydrocarbon containingformation, the method comprising the steps of: injecting a slug solutioncontaining a dispersion of sparingly-soluble sulfonate-metal saltparticles into the hydrocarbon containing formation, where the sparinglysoluble sulfonate-metal salt particle comprises a metal ion salt of analkyl aryl sulfonate, a metal ion salt of a petroleum sulfonate and ahydrophobically modified hydrophilic polymer, where the sparinglysoluble sulfonate-metal salt particle has an average particle sizediameter in a range of from about 50 nm to about 450 nm, where thesparingly soluble sulfonate-metal salt particle is sparingly soluble inwater at room temperature, where the sparingly soluble sulfonate-metalsalt particle is useful for controlling a release of sulfonate;maintaining the slug solution in the hydrocarbon containing formationfor a time in a range of from about an hour to about 1,000 hours; andinjecting water into the hydrocarbon containing formation.
 2. The methodof claim 1 where the alkyl aryl sulfonate comprises dodecyl benzenesulfonate.
 3. The method of claim 1 where the metal ion is selected fromthe group consisting of calcium, magnesium, cobalt, zinc, barium,aluminum, copper, strontium, and combinations thereof.
 4. The method ofclaim 1 where the petroleum sulfonate includes sulfonated benzenoid,cycloaliphatic, paraffinic hydrocarbons and combinations thereof.
 5. Themethod of claim 1 having an average particle size diameter in a range offrom about 50 nm to about 200 nm.
 6. The method of claim 1 where asolubility of the sparingly soluble sulfonate-metal salt particle is ina range of from about 50 parts-per-million (ppm) to about 300 ppm inwater at room temperature.
 7. The method of claim 1 where thehydrophobically modified hydrophilic polymer comprises a polymer madefrom monomers of dimethylaminoethyl methacrylate andcetyldimethylammoniumethyl methacrylate halide. The method of claim 1where the slug solution comprises from 0.05 to 5 weight percent of thesparingly soluble sulfonate-metal salt particles.